The present invention relates to a power window apparatus, and more particularly, to a power window apparatus in which a switch board and a control board are connected via a connector.
In recent years, various motors have been mounted on vehicles to improve convenience. For example, a power window apparatus, which raises and lowers a window glass with a direct current (DC) motor, is mounted on many vehicles. In the power window apparatus, an operation switch is first operated by an operator, so that a motor electronic control unit (motor ECU), which is electrically connected to the operation switch, controls the motor according to an input signal from the operation switch. Torque produced by the motor is then transmitted to the window glass via a mechanical structure, to raise or lower the window glass.
In such a power window apparatus, a board on which the motor ECU is mounted (motor controller) may have a waterproof structure shown, for example, in Japanese Laid-Open Patent Publication No. 2002-13964, to prevent water entry when the vehicle is submerged in water.
In some power window apparatus, a board, on which an operation switch (switch unit) is mounted, and a motor controller are connected via a connector. In a power window apparatus where the connector is arranged on the board of the switch unit, however, the connected parts of the connector and the switch unit often do not have a waterproof structure. If this power window apparatus is submerged in water, water enters into the connected parts of the connector and the switch unit. Such water entry causes leakage current to flow between terminals of the connector. The leakage current may cause the motor ECU to incorrectly recognize its input signal. Particularly, when the motor ECU drives the motor to raise or lower the window glass in response to a low-level input signal (active-low control), the motor ECU may incorrectly recognize its input signal due to water entry.
In more detail, to maintain its input signal at a high-level when the operation switch is not closed, for example, a pull-up resistor is connected to each input terminal of the motor ECU. When, for example, this power window apparatus is submerged in water, water enters into the connected parts of the connector and the switch unit. If this happens, leakage current flows between a terminal for an input signal and a ground terminal. The resistance of a leakage resistor between the two terminals is smaller than the resistance of the pull-up resistor connected to the input terminal. When a leakage current flows, therefore, the motor ECU detects a low-level potential like when the operation switch is closed. This causes the motor ECU to incorrectly recognize that the operation switch is closed when the operation switch is not operated.